The risk of venous thromboembolism (VTE) – the collective name for DVTs and pulmonary embolisms (clots in the lungs) increases dramatically after 4 hours of travel in a plane, car, or otherwise.
Blood clots can form in the lower limbs during long periods of immobility – and can kill if they travel to the lungs.
Although the overall risk is low, being overweight, very tall or short (short is less than 1.6m cough, cough), and women taking oral contraceptives are more vulnerable. Keep in mind also that your risk remains elevated up to 4 weeks after traveling.
